1. Field of the Invention
The invention relates to a disk apparatus having a ramp loading mechanism and a disk medium of such an apparatus. More particularly, the invention relates to a disk apparatus for efficiently performing a servo lead-in at the time when a head is moved to a landing area on a medium and a disk medium of such an apparatus.
2. Description of the Related Arts
In recent years, in a disk apparatus of a disk such as an HDD of 2.5 inches or the like, by providing a ramp loading mechanism, a head is moved to a ramp from a host in an access waiting mode, a drive current of a voice coil motor (hereinafter, abbreviated to xe2x80x9cVCMxe2x80x9d) is shut off, and the apparatus is set into the access waiting mode, thereby suppressing a VCM current consumption in the access waiting mode and extending a life of a battery of a notebook-sized personal computer or the like having the disk apparatus therein. In such a disk apparatus having the ramp loading mechanism as mentioned above, to avoid a head touch at the time of moving the head to a landing area of the medium by the ramp loading, a speed control is generally performed so as to obtain a landing speed which is equal to or less than {fraction (1/10)} of that of the ordinary seeking operation. In a range where it is considered that, when the head during the ramp loading operation is landed onto the medium, the head is come into contact with the medium, the servo lead-in and the reading and writing operations of the data are not performed but the servo lead-in is performed after the head was moved to an area where it is stably floated, a laser beam is moved to a target track so as to enter an on-track state at the completion of the servo lead-in, and the head is positioned to a target sector after that. The operation necessary at the time of servo lead-in is a gain control of an AGC amplifier provided in a read channel and an adjustment of synchronization for a read clock of a PLL. Both of them are performed by using a head preamble of servo information. Particularly, in recent years, since the servo information is also sampled by an A/D converter and processed, it is necessary to detect the servo information a plurality of number of times. The number of servo information recorded on the medium per circumference has been predetermined. It is more preferable to set the number of servo information to a small value in consideration of an efficiency of a data format.
However, in such a conventional disk apparatus having the ramp loading mechanism as mentioned above, since the servo lead-in operation is performed after the head passed through the landing area of the medium, it takes time for the servo lead-in in correspondence to it. To make adjustments of the AGC and PLL which are executed in the servo lead-in operation, it is necessary to read out a plurality of servo information discretely written in the circumferential direction, so that it becomes a factor of extending the lead-in time.
According to the invention, there are provided a disk apparatus in which a servo lead-in time upon ramp loading is reduced and access performance is improved and a disk medium.
According to the invention, there is provided a disk apparatus having a ramp loading mechanism, comprising: a disk medium in which servo information has been written in a landing area on a medium; and a lead-in control unit which performs a lead-in of a servo detecting system on the basis of the servo information when a head is moved from a ramp to the landing area on the medium. Fundamentally, on the disk medium, the second servo information is written in the landing area at an interval which is finer than that of first servo information written in a data area. Therefore, when the head is moved to the landing area on the medium by the ramp loading operation, the lead-in operation is started by using, for example, the second servo information written in the landing area at the fine interval. The lead-in of the servo detecting system can be completed in the landing area. Although it is necessary to sample a plurality of servo information for the purpose of lead-in of the servo detecting system, since the second servo information in the landing area has been written at the finer interval than that of the first servo information in the data area, the servo information of the necessary number can be sampled in a short time. A time necessary for the control of a proper value in the AGC of a variable gain control amplifier (VGC) and the adjustment of a proper value in the PLL are remarkably improved.
On the disk medium, in addition to the same first servo information as that in the data area, the second servo information is written in the landing area at the finer interval. By allowing the first servo information in the data area and the dedicated second servo information to exist mixedly in the landing area as mentioned above, it is sufficient to add the dedicated second servo information into the landing area without changing the writing of the servo information due to an existing servo writer and the servo writing can be easily performed. On the disk medium, it is desirable to write the servo information into the landing area over the whole circumference. The finer the interval of the servo information in the landing area, the time necessary for sampling only the necessary number of servo information can be shortened. A large improving effect of the lead-in operation time can be obtained. On the disk medium, as servo information in the landing area, second servo information having a servo pattern to which position information which can discriminate the position in the circumferential direction has been added is written in the same servo pattern as that of the first servo information in the data area. For example, on the disk medium, a servo pattern to which the position information which can discriminate the position in the circumferential direction has been added is written as second servo information in the landing area into a gray code of the first servo information. As position information of the second servo information, the position in the circumferential direction between sectors based on the first servo information is written or the position in the circumferential direction from index servo information on the medium is written.
The lead-in control unit obtains a deviation time for the first servo information on the basis of the position information of the second servo information upon completion of the lead-in of the servo detecting system based on the second servo information and changes the timing for turning on a subsequent servo gate signal SG by the deviation time, thereby synchronizing it with the first servo information. If the lead-in of the servo detecting system is completed by the sampling of the first servo information in the landing area, since this means that the synchronization has already been established, there is no need to change the lead-in timing. This point results in an advantage obtained in the case where the first and second servo information exist mixedly in the landing area.
On the disk medium, as servo information in the landing area, the second servo information having a servo pattern to which the position information which can discriminate the position in the circumferential direction has been added can be written into a servo pattern different from the first servo information. As a servo pattern different from the first servo information, for example, a servo pattern obtained by excluding burst information from the first servo information, a servo pattern obtained by excluding cylinder information from the first servo information, a servo pattern comprising a preamble and servo mark information, or a servo pattern comprising only the preamble is used as second servo information.
The invention provides a disk medium which is used for the disk apparatus having the ramp loading mechanism and is characterized in that the servo information has been written in the landing area on the medium. That is, it is characterized in that the second servo information is written in the landing area on the medium at the finer interval than that of the first servo information written in the data area. The details of the disk medium are fundamentally the same as those in case of the apparatus.
The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description with reference to the drawings.